From the eighth to the tenth century A.D., Greek scientific and philosophical works were translated wholesale into Arabic. This activity resulted in the incorporation and reorganization of the classical heritage in the new civilization which, using Arabic, spread with Islam. A Greek and Arabic Lexicon presents in an analytical and rationalized way our knowledge of the vocabulary of the translations. It is based on the glossaries included in text editions, both published and unpublished, and on other materials gleaned from various sources. The work is published in fascicules of 128 pages of lexical entries plus indexes of the Greek-Arabic correspondences, of Greek proper names and transliterated words, of variant Greek and Arabic passages, and of the Greek authors cited in the context passages. A Greek and Arabic Lexicon is a reference tool for the study and understanding of Arabic scientific and philosophical language and literature. It facilitates the preparation of future editions of Arabic texts translated directly from the Greek, as well as of works originally composed in Arabic but based on the translations. It contributes to our knowledge of the vocabulary and syntax of Classical and Middle Arabic, of the thought and methods of the translators and of the nature of the translation activity into Arabic methods of the translators and of the nature of the translation activity into Arabic as a whole, and of the way a new vocabulary may develop in an existing language. Moreover, the Greek-Arabic glossary in general and the index of variant Greek passages in particular will assist in future editions of the Greek text of the works translated into Arabic.